The RSA Security report looked at the growth of wi-fi in three key financial centres: London, New York and Paris.

According to the findings wireless access points in London grew by 160% in the last 12 month putting it ahead of the other two cities.

The growth in London was not at the expense of security, found the survey, as the percentage of vulnerable access points fell.

Lock down

The sixth annual survey from RSA of wi-fi found a total of 7130 access points in London compared to 6371 in New York and Paris 827.

In London the vast majority of the access points found (94%) were inside businesses and the remainder were wi-fi hot spots in cafes and libraries that the public can use.

By contrast in New York 15% of access points were for the public and in Paris 11% were open to everyone.

The survey only looked at the three financial centres and did not consider other cities, such as San Francisco, where wi-fi is known to be very popular.

Of the business access points discovered by the RSA survey in London 76% were secured against casual attack and many were using wi-fi's improved encryption system. In New York 64% of business networks were secured and in Paris 71%.

"It is encouraging that almost half of all secured business access points are now using advanced forms of encryption," said Christopher Young, a spokesman for RSA.

"We expect to see these numbers increase as awareness grows around the perils of operating inadequately secured wireless networks," he added.

However, he said, many of the secured networks were using the default settings which may make them vulnerable to determined attackers.